Fire fighting is extremely hazardous and demanding because of extreme temperatures and obscurants that can blind or disable a fire fighter from locating the fire's source or human beings at risk within a burning building. When there are no visible flames, e.g. when alcohol, hydrogen, hydrocarbons, etc. burn, there can be lethally high temperatures caused by gases that burn without visible ignition or flaming. Whether there are visible or invisible flames, nevertheless there can be dense smoke or airborne particulate that makes normal vision impossible. At night or in dark locations, even without extremely high temperatures and even without obscurants, vision is essential to containing a fire or saving a life.
Conventionally, IR vision subsystems for fire fighters have been bulky and integrated with other fire fighting protective equipment worn by fire fighters. They also typically have required an umbilical cord to equipment worn on the body of the fire fighter. Typically, IR equipment is connected with protective body gear referred to herein as a bunker suit typically including or augmented by self-contained breathing apparatus (SCBA).
Other vision systems for fire detection are not designed for hands-free operation as is required of a system used by firefighters that must enter the scene of the fire. For example, U.S. Pat. Nos. 5,422,484 and 5,726,632, the disclosures of which are incorporated herein by reference, disclose various hand-held or pedestal-mounted flame sensors.
So-called night vision systems relying on IR detection and imaging often are useless in the presence within the detector's field of view of such extreme temperatures that the location of a human being or animal, for example, in a burning building goes undetected by a display phenomenon called blooming whereby a high-temperature gas cloud is represented by a color, e.g. white, that tends to wash out critical detail such as a low-temperature human form represented in another area of the display by a different gray scale. Effectively, the high-temperature cloud within view of the IR detector bleaches out needed detail in another area of the display, such as that of a human form. For example, the video systems of U.S. Pat. No. 5,200,827, the disclosure of which is incorporated herein by reference, do not address these problems unique to the firefighting and rescue fields.